Telephone system



July 5, 1932.' G. v. KING ET AL TELEPHONE SYSTEM Original Filed Nov. 8.1929 '7 Sheets-Sheet 1 NSW." 6

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v TELEPHONE SYSTEM Original Filed Nov. 8, 1929 '7 Sheets-Sheet 2MARE/NAL July 5, 193x2- G. v. KING ET Al. 1,866,260

TELEPHONE SYSTEM Origin-al Filedv Nov. 8, 1929 '7 Sheets-Sheet 3 e. K/NG/m/fA/m/ii E A BUNOM/ CONN.

July 5, 1932. 1,866,260

G. V. KING ET AL TELEPHONE SYSTEM Original Fled'Nov. 8, 1929 7Sheets-Sheet 4 July 5, 1932 G. v. KING ET AL 1,866,260

TELEPHONE sYsT'EMf Original Filed Nov. 8, 1929 '7 Sheets-Sheet 5 Afro/MyJuly 5, 1932. G. v, KiNG ET AL 1,866,260

TELEPHONE SYSTEM original Filed Nov. e, 1929 '7 sheets-sheet 6 Iffl/DOLE yFIABQNQM/ A rrd/:way-

July 5., 1932; G. v. KING ET Al. 1,866,260

l TELEPHONE SYSTEM Original Filed Nov. 8, 1929 7 Sheet's-Sheet 7 Ilaffmfom 405 40g/@awww n. 42g- 42a FIG. 7

\F WWE- 40@ 20 09 Uff/5,17@ figg A 429- 428 404 499- -433 gwn-4a G.MK/NG /Nvf/vm/s EA BDNOM/ GERALD V.. KING,

ALBANS, NEW YORK, ASSIGNORS TO BELL TELEPHONE LABORATORIES,

Patented July 5, 1932 OF SPRINGFIELD, NEW JERSEY, AND FELIX A. BONOIVII,OF ST.

INCOBPO- l RATED, OF NEW YORK, N. Y., .A CORPGRATION OF NEW YORK nTELErnoNE sYsfrEM l Application iled November 8, 1929, Serial No.405,603. Renewed .Tune 6, 1931.

This application relates to telephone systems and particularly touniversal cord circuits for miXed service over lines of differentcharacter.

In accordance with this invention a universal cord circuit having ananswering cord and a calling cord is provided with sleeve relaysdiierently responsive to connection with lines of different character.IVith such an arrangement the sleeve relays are operated in dierentcombinations7 each of which is used to set up a diiferent cord circuitcondition. In one instance the cord circuit is maintained in its normalcondition as a local battery feed circuit, wherein a local source ofbattery is connected through supervisory relay to the two cords and thetalking circuit is completed from cord to cord by condensers. In anotherinstance the cord circuit is converted into what may be termed a locallysupervised distant battery feed type of circuit. In this arrangement asupervisory relay in the cord circuit responds to switchhook operationover one of the cords through the agency of battery supplied from adistant point such as over a central oiiice trunk. The local operationof the supervisory relay affects a local supervisory relay and at thesame time controls means to prevent the usual supervisory means at thedistant point from being operated. In a third instance the cord circuitis converted into what may be termed a through circuit without seriesimpedance. In this arrangenient there is a direct connection from thetip of one cord to the tip of the other and a Vdirect connection fromthe ring of one cord to the ring of the other. No impedance such as thewinding of a supervisory relay or a condenser is included in this directpath.

In accordance with another feature of this invention the supervisoryrelay normally connected to respond to switchhook operation over onecord is transferred under a given combination of sleeve relay operationto respend to switchhook operation over the other cord.

' In accordance with :another feature of this invention a flashingrecall means normally arranged lto affect the supervisory signal of onecord is switched to affect the supervisory signal of the other cordunder a given combinat-ion of sleeve relay operation. In accordance withstill another feature of this invention an audible ringing means is madeselective so that upon one hind of connection a ringing tone will betransmitted to the opposite end of the circuit while upon another kindof connection no such ringing tone will be transmitted. v

In accordance with another feature of this invention the operator-sdialing circuit is pro-r videdwith a means selectively operated inaccordance with the kind of connection established for connecting abattery feed bridge or a dry bridge across the answering end of the cordcircuit while the cord is split for dialing over the calling endthereof. v

In accordance with another feature of this invention the ringing currentapplied from the cord circuit when connected to a tie line that does notrequire ringing is automatically cut off and the tie line is cut throughfor vdialing in'response to the operation of the dial. Other featureswill be noted' in the following description. f

The drawings consist of ten figures of circuit diagrams on fivesheetswhich,V arranged according to Fig. 11, illustrate the presentinvention. Fig. l shows the details of the switchboard end of asubscribers line. Fig. 2 shows the switchboard end of an incomingcentral oflice line. Fig. 3 shows the arrangement of a tie line usedbetween two private branch exchange switchboards. Fig. l shows a cordcircuit and Fig. 5 shows the common circuits cooperating therewith, suchas the operators telephone and dialing ycircuit of the click reductioncircuit. Fig. 6 shows the switchboard end of a subscribersline and is aduplicate of Fig. l, it being placed opposite Fig. l to facilitate thedescription. Fig. 7 shows the switchboard end of an outgoing centraloiiice line. Fig. 8 shows the arrangement of a tie line usedvbetween twoprivate branch exchange rswitchboards and is a duplicate of Fig. 3, itbeing placed opposite Fig. 3 as Fig. 6 is placed opposite Fig. 1, inorder to facilitate the description. Figs. 9 and 1 0 taken together showa two-Way repeating tie line which can be used either in cooperationwith the cord circuit of Fig. 4, or with the automatic switches used inan installation of this nature. There are also two additional sheets ofdrawings containing seven additional figures numbered 12 to 18,inclusive, each of which is a schematic of different type of connection.Fig. 12 is a schematic of a station to station connection. Fig. 13 is aschematic of a central office to station connection. Fig. 14 is aschematic of a station to central office connection. Fig. 15 is aschematic of a toll connection. Fig. 16 is a schematic of a connectionsimilar to that of Fig. 12 with an indication of conditions set up inthe operators dialing circuit. Fig. 17 is a schematic of a connectionsimilar to that of Fig. 14 with an indication of conditions set up inthe operators dialing circuit and Fig. 18 is a schematic of a connectionsimilar to that of Fig. 13 with an indication of conditions set up inthe operators dialing circuit.

In general, the cord circuit of Fig. 4 consists of an answering plug 400and a calling plug 401. The answering plug 400 is invariably used toanswer an incoming call made over any one of the lines, such as those ofFigs. 1, 2 or 3. The calling plug 401 is used to complete the connectionto such lines as those illustrated in Figs. 7, 8 and 9. Associated withthe answering plug 400 is the answering supervisory lamp 402 andsimilarly associated with calling plug 401 is the calling supervisorylamp 403. Under circumstances to be hereafter described, relay 404 maybe termed the answering supervisory relay and relay 405 may be termedthe calling supervisory relay.

The .sleeve of the answering plug 400 eX- tends in series through thewindings of two sleeve relays 406 and 407. Relay 406 is marginal andwill only be energized when the plug 400 is inserted in a jack whosesleeve is connected to a low resistance relay, such as that shown inFig. 1. Then the plug 400 is inserted in a jack whose sleeve isconnected to a high resistance relay, such as that shown in Fig. 2,marginal relay 406 will fail to operate. Relay 407, however, operates ineither case. It should be noted that a noninductive resistance 408 isconnected in shunt of the two relays 406 and 407. This is the usualarrangement to prevent the operator from being shocked by an inductivedischarge when she removes the plug 400 from a line jack.

In a similar manner the sleeve of plug 401 extends in series throughrelays 409 and 410. Relay 409 like relay 406 is marginal and will onlybecome energized when the plug 401 is placed in a jack whose sleeve isconnected to a low resistance relay, such as that in Fig. 6.Non-inductive resistance 411 is connected in shunt of relays 409 and 410for the same purpose as described in connection with re`J sistance 408.

Station to station call Fig. 12 is a schematic of the type of circuitemployed for a station to station connection. 1t is commonly known as abridged impedance cord circuit. The battery feed is local, that iscurrent for talking purposes is supplied from within the cord circuitand the talking conductors are conductively separated by condensers.

The subscriber at substation removing his receiver from its hook causesthe energization of the usual line relay 101 which in turn causes theillumination of line lamp 102. The operator inserts plug 400 in jack 103thus completing a circuit through relays 104, 406 and 407. Relay 104being of low resistance causes the energization of both relays 406 and407. Relay 104 becoming energized places ground on conductor 105 inorder to niark the line as busy in the connector banks to which theconductors 106 extend. At the same time the Ground connection onconductor 105 causes the energization of the cutoff relay 107 wherebythe line relay is cut oft' and the talking conductors from thesubscribers station are connected through to the tip and ring contactsof jack 102.

Battery current is supplied to the calling substation 100 over thefollowing path from battery, lower winding of retardation .coil 413,back Contact and lower outer armature of relay 414, conductor 415,contacts 416 and 417, conductor 418, lower winding of relay 404, normalcontacts of the lower contact set of ringing key 419, ring contact ofplug 400, ring contact of jack 103, front contact of lower armature ofcut-off relay 107, through the loop of substation 100, inner upperarmature and front Contact of cut-off relay 107, tip contact of jack103, tip contact of plug 400, normal contacts of the upper contact setof ringing key 419, upper winding of supervisory relayv 404, conductor420, contacts 421 and 422, conductor 423. upper outer armature and backcontact of relay 414, upper winding of retardation coil 413 to ground.The receiver being ofi' its hook at substation 100 current flows throughthis circuit and causes the energization of answering supervisory relay404.

The operator now establishes a talking connection with the callingsubscriber by operating the listening key 424, whereby a connection ismade between the conductors of the cord and the operators telephone setas follows: tip conductor 420, contacts 421 and 422, conductor 423, backcontacts of the outer upper armature of relay 414, condenser 425, backcontact and inner upper armature of relay 414, contacts 426 and 427 oflistening key 424, conductor 428, conducto-r 500, normal contacts of theinner upper armature of fifi" relay 501, conductor 502, windings 503 and504 of the operators telephone set induction coil, condenser 505,conductor 506, back contact and outer lower armature of relay 507,conductor 508, normal contacts of the outer upper armature of relay 501,conductor 509, conductor 429, contacts 430v and 431 of key 424, innerlower armature and back Contact of relay 414, condenser 432, backcontacts and lower outer armature of relay 414, conductor 415, contacts416 and 417 and thence to ring conductor 418.

The operatorls receiver 510 is effectively bridged across winding 503 ofthe operators telephone set induction coil. Such connection may betraced from the lower terminal of winding 503, conducto-r 502, conductor511, conductor 433, contacts 434 and 435 of key 424, conductor 436,conductor 512, contacts 513 and 514 of key 515, primary wind ing 516 ofthe input transformer for the operators click reduction circuit,contacts 517 and 518 to the upper terminal of winding 503. Voicecurrents in transformer winding 516 will be translated through theaudion 519 and output transformer 520 to the two output conductors 521and 522. Conductor 521 extends over contacts and 524, through sleeve ofjaclr 525, sleeve of plug 526, receiver 510, sleeve of plug 527, sleeveof jack 528 to conductor 522.

The transmitter 529 is in a circuit from battery, winding of relay V530,tip of jack 531, tip of plug 532, transmitter 529, tip of plug 533, tipof jack 534 to ground. The winding 535 of the operators set inductioncoil is in parallel with the transmitter and will translate voicecurrents generated by said transmitter into the cord circuit, throughthe agency of windings 503 and 504 connected over conductors 502 and 506to the tip and ring conductors of the cord as hereinbefore described.

The operator now challenges the calling subscriber and learning that aconnection is desired to the substation 600 males the usual busy test bytouching the tip of plug 401 to the sleeve of jack 601. If the line ofsubstation 600 is idle, ground will be found on i sleeve of jack 601 andno busy test indication will be Oiven to the operator. If, however, thisline is busy a battery potential will be found on the sleeve of jack 601which will be communicated over the tip of plug 401,

- upper normal contacts of ringing key 437, in-

ner upper armature and back contactof relay 438, conductor 439,conductor 536, winding of polarized relay 537 to ground. Relay 537 willrespond to this connection and will in turn establish a connection frombattery, through resistance 538 shunted by condenser 539, armature andfront contact of relay 537, winding 540 of the busy test induction coilto ground. The current built up in winding 540 will induce a transientcurrent in the secondary winding 5'41 which being bridged across thewinding 503 of the operators set induction coil will manifest itself asa click in the operators receiver.

Let it be assumed that the line of substation 600 is found to be idle.Then plug 401 will be inserted in jack 601 and since relay 602 is of lowresistance it will become energized along with both relays 409 and 410in series therewith. Relay 410 becoming energized causes theenergization of relay 438 whereupon a circuit is established frombattery, inner lower armature and front contact of relay 438, contacts440 and 441, conductor 442, lower winding of relay 443, back contact andlower outer armature of relay 444, front contact and armature ofanswering supervisory relay 404, resistance 445 to ground. Relay 443becomes energized in this circuit.

Since relay 409 has become energized a circuit is now established frombattery, calling supervisory lamp 403, lower outer armature and frontContact of relay 409, back contact and armature of calling supervisoryrelay 405, alternate contacts of the innermost upper armature of relay406 to ground. Sup-ervisory lamp 403 becomes illuminated to indicatethat the called party has not yet removed his receiver from its hook.

Relay 443 now becomes locked in a circuit from ground, its inner upperarmature and front contact and its upper winding, conductor 447, frontcontact and inner lower armature of relay 409, conductor 442 and thenceto battery over the circuit heretofore traced. 4t the same time batteryon conductor 442 is extended through the inner lower armature and frontcontact of relay 409, the inner upper armature and back contact of relay446, winding of relay 448, conductor 449, front contacts and upper outerarmature of relay 412 to ground. Relay 448 becomes energized in thiscircuit and connects ringing current to the called line.

This current flows over a path from ground, front contact and the innerupper armature of relay 448, contacts 450 and 451, front contact andinner upper armature of relay 438, upper normal contacts of ringing key437, tip of plug 401, tip of jack 601, through the front Contact andupper armature of cut-ofi' relay 603, over the loop of substation 600,lower armature and front contact of relay 603, ring contact of jack 601,ring of plug 401, lower normal contacts of key 437, contacts 452 and453, lower armature and front contact of relay 448, windingof ringingcut-0E relay 454. upper outer armature and front Contact of relay 448 tothe source of ringing current.

1t should be noted at this point that relay i 446 has a circuit fromground, its upper winding, resistance 455 and thence over the frontContact and inner lower armature of relay 409 to battery on conductor442. However, the upper winding of relay 446 is shortecircuited throughits own upper outer armature and back contact and the back contact ofrelay 454 to ground so that relay 446 cannot relay 414, condenser' 432,back contacts and outer lower armature o' relay 414, conductor 415,contacts 416 and 417 and thence to conductor 418 from whence it finds apath through the calling substa tion to ground connected to the upperwinding of retardation coil 413 previously described. Thus, during thetransmission of ringing current to the called subscribers line a ringingtone is given to the calling subscriber.

The ringing` current iowing in the called subscribers telephone isinsufficient to cause the energization of ringing cut-0E relay 454 untilthe subscriber thereat removes his receiver' from its hook. At this timerelay 454 becomes energized and removing ground from the back contact ofthe upper outer armature of relay 456 opens the short circuit across theupper winding of relay 446 so that this relay now becomes energized inseries with resistance 455 to battery on conductor 442 through its innerupper armature. Relay 446 opens the circuit of relay 448 and this relaynow becomes deenergized.

Thereupon a talking circuit for substation 600 is established fromground, upper winding of answering supervisory relay 405, back contactand inner upper armature of relay 414, contacts 426 and 427 conductor428, conductor 500, normal contacts of the inner upper armature of relay501, conductor 511, conductor 433, contacts 434 and 459, back Contactand inner upper armature of relay 448, contacts 450 and 451, frontcontact and inner upper armature ot relay 438, upper normal contacts ofkey 437, tip of plug 401, tip of jack 601, over the loop ot substation600, ring of jack 601, ring of plug 401, lower normal contacts of key437, contacts 452 and 453, lower armature and back Contact of relay 448,contacts 456 and 457, conductor 458, conductor 542, normal contacts ofthe upper outer armature of relay 501, conductor 509, conductor 429,contacts 430 and 431, inner lower armature and baclr contact of relay414, lower winding of answering supervisory relay 405 to battery., Thecircuit just traced is one which is established while the operator hasthe listening key 424 operated. When the operator has restored key 424to normal then the circuit extends directly from contact 426 to contact459 to the tip of the cord and from the ring of the cord directly fromcontact 456 to contact 431 so that in either case battery and groundthrough the windings of relay 405 are connected to the tip and ring ofplug 401 and thence to the called subscribers line.

lVhen the relay 405 becomes energized in the circuit just described,answering super- Visory lamp 403 becomes dark thus indicating to theoperator that the called subscriber has answered.

TWhen the conversation has termin ated and the called subscriberreplaces his receiver, relay 405 becomes deenergized and again closes acircuit for lamp 403 which becomes lighted. lf at the same time thecalling subscriber replaces his receiver', then answering supervisoryrelay 404 becomes deenergized and returning its armature to normalestablishes a circuitrom ground, resistance 445, armature and backcontact of relay 404, front contact and lower armature of relay 406,answering supervisory lamp 402 to battery. Lamp 402 becomes lighted toindicate that the calling subscriber has hung up. At the same time theground for the energization of answering supervisory lamp 402 isextended through the lower inner armature and front contact of relay443, normal contacts of the inner lower armature of relay 444, contacts460 and 461, winding of relay 444, front contact and inner lowerarmature of relay 409 to battery on conductor 442. Relay 444 becomesenergized in this circuit and locks to ground through its inner lowerarmature and front Contact.

lt the calling subscriber does not again take his receiver olf its hookbefore the operator has talren the connection down, the energizationoli' relay 444 has no eliqect. lf, on the other hand, the callingsubscriber wishes to recall the operator, he then reino-ves his receiverfrom its hook wl'iereupon relay 404 again becomes energized and acircuit is established in parallel with lamp 402, from the armature andfront Contact of relay 404, the lower cuter armature and front contactof relay 444, flashing recall lead 462, normal contacts or the upperarmature ot relay 463, upper winding ot relay 464 to battery. he upperwinding of relay 464 is of low resistance and while it is in shunt oflamp 402 it reduces the current flow therethrough below the amountnecessary for illumination of the lamp. Relay 464 is energized. in thiscircuit and upon operating its armature closes a circuit for relaythrough the interrupter 465. lVhen the interrupter closes this circuit,relay 463 will become energized and by moving its upper armature opensthe lead 462 so as to remove the shunt from about lamp 402 therebyallowing it to become fully illuminated. At the same time a circuit isclosed through the lower high resistance winding of relay 464 in serieswith the upper low resistance winding so that relay 464 is maintainedenergized as long as the circuit through lead 462 is effective. Vihenthe interrupter 465-moves to open segment then relay 463 is deenergizedand the lamp 402 is again shunted by the low resistance winding of relay464. lt will thus be seen that relay 463 responds to the interrupter 465and that the lamp 402 will flash accordingly. Through its low-erarmature relay 463 closes a circuit for magnet 467 which acts as anaudible sounder. Thus on a recall there is both a visible and audiblesignal given to the operator.

Nhen the operator answers the recall by operating listening key 464, sheopens the circuit of relay 444 at contacts A460 and 461 so that thisrelay now returns to normal and will so remain until the connection hasbeen taken down. I

On arecall such as that just described the called party may be signaledby `the operation of ringing key 437, or the operator instead may takethe plug 401 out of the jack 601 momentarily so as to restore relay 446to its normal condition.

Central ao@ to station @all Fig. 13 is a schematic of the type ofcircuit` employed on an incoming .central ofice call destined tor alocal station. This is commonly known as a distant battery feed locallysupervised cord circuit. Note that a bridge is interposed between thelocal supervisory relay and the source of current at the central oiiice.Thus the central oliice battery is used for talking purposes and forlocal signaling without disturbing the supervisory relay at the centralotlice. Villien the local station receiver is oil the hook the'bridge isincreased in impedance so as not to affect transmission.

0n a call from the central oiiice over the trunk shown in Fig. 2,ringing current will iow over the upper outer armature and back contactVof relay 200, lower winding of ringing relay 201, condenser 202, lowerarmature and back contact of relay 203 to the line wire 204. Relay`201responds to this currentand locks in a circuit trom ground, inner upperarmature and back contact of relay 200, upper winding of relay 201,front contact and inner lower armature of relay 201, outer lowerarmature. and contact of relay 201 to battery. Through the front contactrand outer lower armature ot relay 201 line lamp 205 is energized so asto display a calling signal to the operator. `rThe battery connectionfor the energization of the upper winding of relay 201 also extends tothe winding of relay 203 which now becomes energized and through itslower armature and front con- .and therefore relay tact short-circuitsthe lower winding of relay 201.

The operator handling the cord circuit ot Fig. 4 will insert plug 400 injack 206 whereupon a circuit is established from ground, winding ofrelay 200, normal contacts of the lower armature of relay 200, ringcontact of jack 206, ring of' plug 400, lower normal contact-s ofringing key 419, back contact and outermost upper armature of relay 406,back contact and outermost upper armature of relay 409, conductor 415,outer lower armature and back Contact of relay 414, lower winding ofretardation coil 413 to battery and ground. Relay 200 is energized inthis circuit and in moving its armatures to their operated positions,transfers the circuit of relay 200 from the ring of jack 206 to thesleeve of jack 206 soV that relay 200 now remains operated in serieswith relays 406 and 407. Relay 200 being of high resistance limits thecurrent iowing in this circuit so that relay 406 does not becomeenergized.

' Upon the energization of relay 200 a circuit is closed Jfromthe lineconductor 207 outer Lipper armature and front contact of the relay 200,alternate contacts of the upper armature of relay 203, resistance 208 toconductor 204. Thus a shunt is momentarily placed across the trunk inorder to trip the machine ringing arrangement at the central oiiice. Theenergization of relay 200 at the same time opens the circuit for theupper winding of relay 201 so that this relay becomes deenergizedcausing in turn the deenergization of relay 203. This relay, however,being slow to release maintains a circuit through resistance 208 justdescribed for a length of time suilicient to insure tripping of themachine ringing. It then becomes deenergized and closes the line wire207 to the tip of jack 206 and the wire 204 through to the ring of jack206.

In this instance relay 407 is energized, but relay 406 remains in itsnormal condition 412 becomes energized and closes a circuit from theouter upper armature and front Contact of relay 412, the back contactand next to outermost upper armature of relay 406, winding of relay 414.to battery and ground. Relay 414 become.C

' 415, contactsy 416 and 417 to ring conductor 418. Thus a talkingconnection between the central olice trunk and the operators set isestablished.

Since battery and ground are supplied from the central otlice trunk acircuit is estab- 1 lished from conductor 207, upper outer armature andback contact of relay 200, normal contacts of the upper armature ofrelay 203, tip conductor of jack 206, tip Contact of plug 400, uppernormal contacts of ringing key 419, inner upper armature and frontcontact of rela-y 412, the next to innermost upper armature and backcontact of relay 406, middle winding of retardation coil 413, upperouter armature and back contact of relay 443, outermost upper armatureand back contact of relay 406, lower normal contacts of ringing key 419,ring contact of plug 400, ring contact of j ack 206, lower armature andfront contact of relay 200, lower armature and back contact of relay 203to conductor 204. Thus the middle winding of retarda-k tion coil 213 isbridged across the central office trunk to operate the supervisory relayat the central otfice. The answering -cord supervisory relay 404 is notoperated at this time.

The operator now answers the incoming central oilice call and learningthat the subscriber at substation 600 is wanted, makes the usual busytest by touching the tip of plug 401 to the sleeve of jack 601. Uponlearning that the line to substation 600 is idle, she will insert theplug 401 into jack 601 thereby causing the energization of relays 602,409 and V412. Relay 448 becomes energized as hereinbefore described andapplies ringing current tothe line of substation 600.

In this case it should be noted that relay 443 has not become energizedas yet and hence the ringing current applied to condenser 466 finds noreturn path so thata ringing tone is not transmitted in this instance.

When the subscriber at substation 600 removes his receiver from itshook, relay 454 is energized and rela,v 446 responds as before. Relay448 is returned to normal and a talking circuit is now established fromthe tip of plug 400, through the upper winding of relay 404, conductor420, contacts 421 and 422, conductor 423, front contact and inner upperarmature of relay 414, contacts 426 and 459 (assuming that the operatorhas restored key 424), back Contact and inner Lipper armature of relay448, contacts 450 and 451, front contact and inner upper armature ofrelay 438, upper normal contacts of ringing key 447, tip of plug 401,tip of jack 601, over the loop of substati n 600, ring of jack 601, ringof plug 401, lower normal contacts of ringing key 437, contacts 452 and453, lower armature and back contact of relay 448, contacts 456 and 431,inner lower armature and front contact of relay 414, conductor 415,contacts 116 and 41T, conductor 418, lower winding of supervisory relay404, lower normal contacts of ringing key 419 to the ring of plug 400.Thus talking current is supplied to substation 600 from the centraloilice trunk through the windings of supervisory relay 404.

Supervisory relay 404 now becomes energized and establishes a circuitfrom ground, resistance 445, armature and front contact of relay 404,lower outer armature and back Contact of relay 444, lower Winding ofrelay 443, conductor 442, contacts 441 and 440, front Contact and innerlower armature of relay 438 to battery. Relay 443 becomes energized inthis circuit and inserts resistance 468 in series with the middlewinding of retardation coil 413.

It should be emphasized at this point that when the substation 600 isbridged across the line and uses battery from the central olice trunkthat the bridge also across the line and between the relay 404 and thecentral oilice consists of a high impedance including the middle windingof retardation coil 414 and the resistance 468. When, however, thebridge of substation 600 is removed so that supervisory relay 404 cannotbe energized by the central oHce battery, then the impedance of thebridge between relay 404 and the central office is reduced through theshort-circuiting of resistance 468.

This type of circuit may appropriately be called local superviseddistant battery feed circuit since the only result of switch hookmovement at substation 600 will be to signal the operator at cordcircuit 400 without disturbingV the supervisory signal at the centralofiice from which the battery supply is derived.

If after the subscriber at substation 600 has answered and the bridgeacross thel trunk between the supervisory relay 400 and the centraloiiice has been increased in its impedance through the introduction ofresistance 468, such subscriber wishes to recall the operator he may doso by depressing his receiver hook once.

The depression of the receiver hook at substation 600 results in thedeenergization of relay 404 whereupon a circuit is established fromground, resistance 445, armature and back contact of relay 404, innerlower armature and front contact of relay 443, normal contacts of theinner lower armature of relay 444, contacts 460 and 461, winding ofrelay 444, front contact and inner lower armature of relay 409 tobattery on conductor 442. Relay 444 becomes energized in this circuitand locks over its inner armature and front contacts so that when theswitch hook at substation 600 is again lifted and relay 404 is againenergized, t-he flashing recall circuit through the front contact andouter lower armature of relay 444 becomes effective. The operator inanswering the recall operates key 424 and through the opening ofvcontacts 460 and 461 restores relay 444 to normal.

ln connection with this type call from an incoming central oilice trunkto a station it Y should be emphasized that the flashing recall circuitoperates in response to a recall made over the calling plug 401 insteadof over the answering plug 400 as previously described and that therelay 404 which in the first instance responded to switch hook operationover the answering plug` 400, in this instance type of cord circuit, forin this cas-e the automatic flashing recall feature is not used.

Hence the bridge between the local supervisory relay is changed indirect response to the local supervisory relay.

TWhen the subscriber at substation 100 wishes to get a connection to thecentral office he removes his receiver as usual and causes the lightingof line lamp 102. The operator inserts plug 400 in ack 103 with theresults hereinbefore noted. l She will then, upon instruction of thesubscriber at substation 100, insert plug 401 in jacl; 700 of theoutgoing central office line. The sleeve relay 701 associated with thisoutgoing trunk is of high resistance so that'relay 410 will becomeenergized in series with relay 701, but relay 409 will fail to operate.Relay 414 operates over the baclt contact and middle upper armature ofrelay 409, lower outer armature and front contact of relay 438 toground. Due to the failure of relay 409 to operate, the ringing relay448 cannot become energized and hence a bridge will be immediatelyestablished across conductors 702 and 703 follows: conductors 702, frontcontact and upper armature of relay 701, tip conductor of jaclr 700, tipconductor of plug 401, upper normal contacts of ringing lrey 437, innerupper armature and front contact of relay 438, contacts 451 and 450,inner upper armature and baclr contact of-relay 448, contacts 459 and434, conductor 433, conductor 511, normal contacts of the inner upperarmature of relay 501, conductor 500, conductor 428, contacts 427 and426, inner upper armature and front contact of relay 414, front contactand outer upper armature of relay 438, innermost upper armature andbaclr contact of relay 409, middle winding of retardation coil 413,upper outer armature and baclr con tact of relay 443, outermost upperarmature and back contact of relay 409, conductor 415. front contact andinner lower armature of relay 414, contacts 431 and 430, conductor 429,conductor 509, normal contacts of the upper outer armature of relay 501,conductor 542, conductor 458, contacts 457 and 456, baclr contact andlower armature of relay 448, contacts 453 and 452, lower normal contactsof-ringing lrey 437, ring of plug 401, ring o f jaclt 700, inner lowerarmature and front contact of relay 701 to conductor 703. This bridgeconsisting essentially of the middle winding of retardation coil 413thrown across conductors 702 and 703 will signal the central oiceattendant.

W'hen the connection is completed at the central office, battery andground are connected to conductors 703 and 702 respectively and willflow over a circuit which may be traced from tip of plug 401, uppernormal contacts of ringing lrey 437,inner upper armature and baclrcontact of relay 438, contacts 451 and 450, inner ripper armature andback contact of relay 448 (and now assuming thatY the operator hasrestored lrey 424 to normal) through contacts 459 and 426, inner upperarmature and front contact of relay 414, conductor 423, contacts 422 and421, conductor 420, upper winding of supervisory relay 404, upper normalcontacts of ringing lrey 419, tip of plug 400 and thence through theloop of substation 100, ring of plug 400, lower' normal contacts ofringing lrey 419, lower winding of supervisory relay 404, conductor 418,contacts 417 and 416, conductor 415, front contact and inner lowerarmature of relay 414, contacts 431 and 456 of ley,424, baclr contactand lower armature of relay 448, contacts 453 and 452, lower normalcontacts of ringing lrey 437 to ring of plug 401. Relay 404 will becomeenergized through the current flowing through substation and byoperating its armature will establish a circuit from ground,` resistance445, armature and front contact of relay 404, lower armature and baclrcontact of relay 444, lower winding of relay 443, conductor 442,contacts 441 and 440, contact and inner lower armature of relay 438 tobattery. Upon the energization of relay 443, resistance 438 is placed inseries with the middle winding of retardation coil 413 so that thebridge across the central oflice line between the supervisory relay 404and the centraloflice is now of high iinpedance so as not to interferewith the talking currents.

1f the subscriber at station 100 should replace his receiver then relay443 will be released and the bridge across the central office trunlrwill be reduced to the middle winding of retardation coil 413 alone. Atthe same time a circuit will be established from ground, resistance 445,armature and back contact of relay 404, front contact and lower armatureof relay 406, supervisory lamp 402 to battery. lf the subscriber shouldrecall by again taking his receiver ed the hook, relays 404 and 443 willrespond and lamp 402 will go out. Thus on this type of connecllt) tionwherein a subscribers line is connected to the answering cord and thecentral oilice trunk is connected to the calling cord, the supervisorylamp will respond directly to switch hook operation and not to theautomatic iiashing recall circuit as hereinbefore described.

Toll connection Fig. 15 is a schematic of a toll type connection intowhich the present cord circuit may be converted under appropriatecircumstances. Note that it is very simple, consisting of a pair ofconductors making a through connection from the calling line to thecalled line.

It may happen with this type of installation that a toll type connectionis needed as when a call coming in over a tie line is destined to beextended over another tie line. Let us assume an incoming call on thetie line of Fig. 3. Ringing current coming over conductor 300 passesover the outermost upper armature and back Contact of relay 301, winding302 of repeating coil 303, lower winding of relay 304, lower winding 305of repeating coil 303, back Contact and middle upper armature of relay301 to conductor 306. Relay 304 is energized in this circuit and throughits lower outer armature establishes a connection for signal lamp 307.Relay 304 locks in a circuit from battery, back contact and armature ofrelay 308, back contact and upper outer armature of relay 309, backcontact and lower outer armature of relay 301,

upper winding of relay 304, front Contact and inner lower winding ofrelay 304 to ground. Thus line lamp 307 will remain lighted until thecall is answered in the usual way.

The operator noting the call will insert plug 400 into the through jack310 whereupon a connection is established from ground through thewinding of relay 301, sleeve of jack 310, sleeve of plug 400 and thencethrough relays 406 and 407. Relay 301 being of high resist-ance causesthe operation of relay 407, but not the operation of relay 406.

The operator learning that a connection is desired to another distantprivate branch eX- change will insert plug 401 into jack 300 whereuponrelay 801 will be energized in series with relays 409 and 410 causingthe operation of relay 410 alone. Relay 414 is operated over the backcontacts of both relays 406 and 409.

Thus in this case neither of the marginal relays 406 or 409 is operated.rThis results in a toll type cord wherein a direct connection may betraced from the tip of plug 400 to the tip of plug 401 as follows: tipof plug 400, upper normal contacts of ringing key 419, inner upperarmature and front contact of relay 412, next to the innermost upperarmature and back contact of relay 406, in-

nermost Lipper armature and back Contact of relay 409, outer upperarmature and front Contact of relay 433, conductor 423, front contactand inner upper armature of relay 414, contacts 426 and 459, backcontact and inner upper armature of relay 443, contacts 450 and 451,front contact and inner upper armature of relay 433, upper normalcontacts of ringing key 437 to the tip of plug 401.

1n a similar manner a direct connection may be traced from the ring ofplug 400 to the ring of plug 401 as follows: the ring of plug 400, thelower normal contacts of ringing key 419, back Contact and outermostupper armature of relay 406, back contact and outermost upper armatureof relay 409, conductor 415, front contact and inner lower armature ofrelay 414, contacts 431 and 456, back Contact and lower armature ofrelay 443, contacts 453 and 452, lower normal contacts of ringing key437 to the ring of plug 401.

In a connection of this type, if the operator is needed her attentionmay be attracted as follows: Let it be assumed that the operator at thedistant end of the trunk in Fig. 3 impresses ringing current on theconductors 303 and 306. This ringing current will flow from conductor300, over the outermost upper armature and front contact of relay 301,conductor 311, winding of relay 312 and condenser 313, conductor 314,front Contact and middle upper armature of relay 301 to conductor 306.Relay 312 responds to this ringing current and by operating its armaturecloses a circuit from ground, inner upper armature and front contact ofrelay 301, upper winding of relay 304, lower outer armature and frontcontact of relay 301, front contact and inner lower armature of relay301, resista-nce 315 to battery. Relay 304 responds in this circuit andcauses the lighting of line lamp 307 as before. This line lamp acts as asupervisory means during the maintenance of a connection over thistrunk. As soon as the ringing current applied to conductors 303 and 306is removed, relay 312 will restore its armature to normal and the upperwinding of relay 304 will be short-eircuited.

The line lamp 802 may be illuminated in the same manner to call theattention of the operator.

Tie Zine to station connection Fig. 13 is a schematic of a tie line tostation connection.

In the case of a. call coming over the tie line of Fig. 3 intended for astation such as substation 600, such call will be answered as justdescribed. The operator, however, upon being informed that station 600is wanted will transfer the plug 400 from jack 310 to jack 316. This isfor the purpose of getting a better source of talking current than couldbe supplied over the long loop of the tie line.

The sleeve resistance in the case of jack 316 is the same as that; ofjack 310, i. e., relay 309 is of high resistance so that the connectionin this instance will be the same as a central oce to station call.Battery and ground are supplied to the tip and ring of jack 316 aslTielz'neto central oyce Zz'ne connection Fig. 14 schematicallyrepresents a tie line to central oiiice connection.

Assume an incoming call on the tie line of Fig. 3 destined for thecentral olce over the outgoing trunk of Fig. 7. The operator being toldthat such a connection is wanted will transfer the plug 400 from jack310 to trunk jack 320. This jack has a low resistance sleevein relay 308so that the connection now set up will be similar to the connectionheretofore described between the substation 100 and the central otliceline, Fig. 7 A bridge consisting of retardation -coil 321 will be placedacross the line to simulate a receiver ofi' the hook and will cause theenergization of the supervisory relay 404 as here-A tofore described.

'Station to repeating tz'e Zine connection over conductors 1000 and1001. Access mayA also be gained to this trunk over the tip, ring andsleeve conductors 1002, 1003 and 1004 through automatic'switches (notshown) to extend a connection also to a distant exchange over tip andring conductors 1000 and 1001. Calls incoming from a distant exchangewill be extended over the tip, ring and sleeve conductors 1005, 1006 and1007 to an incoming selector (not shown) lfrom which connection may beestablished to stations Within this PBX.

For purposes of disclosing the present Vinvention only one type ofconnection will .be explained, i. e., a connection from .jack 900extending out over the tip and ringconductors 1000 and 1001 to a distantPBX.

lVhen a subscriber desires a connection to a such K as distant PBX whichwillrequire the use of the trunk of Figs. 9 and 10, plug 400 is insertedin jack 103 and plug 401 is inserted in jack 900. VSleeve relay 901operates in the sleeve circuit and since this relay 901 is of lowresistance the type of cord circuit established will be similar to thatof Fig. 12,

i. e., both supervisory relays 404 and 405 will become effective andthetrunk relay 414 will not operate. serted in ack 900 ringing current willbe applied to the trunk as hereinbetore described on the operation ofrelay 448.

`Ringing current will ow over the tip of jack 900, the upper armatureand back contact of relay 902, high resistance ringing relay 903, backcontact and inner lower armature of relay 902`to the ring of jack 900.Relay 903V will be energized in this circuit and will cause theoperation'ot relay 904. Upon the operation ot relay 904 a. circuit willbe established from ground, the front contact and inner lovver armatureof relay 901, conductor 908, innermost lower armature and front contactsof relay 904, winding of relay 904 and in parallel therewith the windingof relay 902 to battery and ground. This operates the cut-ofi relay 902and causesthe deenergization of relay 903. Relay 902 in operatingestablishes a circuit from ground, through its iront Contact and middlelower armature, the winding of relay 1008 to battery. Relay 1008operates and places a ground on conductor 1004 to mark this trunk in theswitches having access to conductors 1002, 1003 and 1004 as busy.

Assuming` that the tie line at the distant end of this trunk is aduplica-teef the one shown in Figs. 9 and 10, a ,circuit will now beestablished from battery, through the upper winding of the relay such as1009, the normal contacts ot the middle upper arma-Y ture of the relaysuch as 1010, the outermost lower armature and back Contact of relaysuch as 904, back contact and middle upper armature of relaysuch as1011, ring conductor y1001, thence through the middle upper armature andback contact of'relay 1011, alternate contacts of the outermost lowerarmature of relay 904, lower winding ot relay 905, normal contacts ofthe lower armature of relay 906, upper winding of relay 905, alternatecontacts of the upper armature ot' relay 904, bacli Contact andoutermost upper armature of re lay 1011, conductor 1000 and thence atthe distant end from the outermost upper armature and back contact ofrelay such as 1011, back contact and upper armature of relay 904, Vbackcontact and inner upper armature ot' relay such as 1010, lower windingof relay such as 1009 to ground. Thus by the operation of relay 904 abridge includingA the two windings of supervisory relay 905 is thrownacross the trunlrto operate the line relay at the distant end. Relay Assoon as plug 401 is inV 905 by operating its Contact extends groundoperated the talking and dialing key 424' and established a conditionschematically shown in Fig. 16. She now operates the dial 548, whereuponthe oil-normal contact-.will establish a connection from ground toconductor 549, lower winding of relay 507 to battery. Relay 507 operatesand extends the ground on conductor 549 tothe winding of relay 547 whichvnow vbecomes operated and through its front Contact and upper armaturegrounds the upper winding of relay 507. Relay 547 also closes a circuitfrom ground, through its contacts 550 and 551 to the winding of relay501.

A connection is now established from ground, innermost upper armatureand front contact of relay 507, winding of low resistance relay 546,conductor 552, conductor 469, contacts 470 and 471, contacts 472 and 473controlled by relay 446, lower winding of relay 446, front contact andinner lower armature of relay 409 to Ybattery on conductor 442. Relay446 becomes operated in this circuit and by openine the circuit for thewinding of relay 448 at the upper inner armature and back contact cutsoff ringing current being transmitted tothe trunk of Fig. 9. Upon theoperation of relay`446, the connection from the relay 546 is extendedthrough the front contact and lower armature of relay 446 to the sleeveconductor of plug` 401.

This connection maintains relays 409 and 410V operated and throws a lowresistance O'round connection in parallel with the winding of relay 901so that this relay now being practically short-circuit-ed restores itsarmatures to normal.

A circuit may now be traced from ground., 'front contact and armature ofrelay 907, conductor 908, inner lower armature and back contact of relay901 to the windings of relays 909 and 906 in parallel. Relay 909operates directly in this circuit and relay 906 locks through its frontcontact and inner upper armature directly to conductor 908 so that whenrelay 901 again becomes operated relay 906 will remain actuated andrelay 909 will restore its armatures to normal.

Relay 546 has become operated inthe circuit described and closes a.circuit from ground, front contact and armature of relay 546, winding ofrelay 545 to battery and ground. Relay 545 connects the windingof relay544 to the two upper armaturesof relay 501 so that the condition nowobtained is as follows; the windings ot' relay 405 are connected throughthe winding ot relay 544, and a bridge including the dial contacts of fbut relay 907 being dial 548 is, thrownacross the tip and ringconductors 1000 and 1001.

Thecircuit for relay 405 may be traced trom'ground, the upper winding otrelay 405, the back Contact and inner upper armature of relay 414,contacts 426 and 427 of key 424, conductor 500, front Contact and innerupper armature of relay 501, inner upper armature and iront contact ofrelay 545, winding? ot relay 544, iront contact and upper outer armatureot relay 545, upper outer armature and iront contact of'relay 501,conduct-or 509, conductor 429, contacts 430 and 431 of key 424, innerlower armature and back Contact of relay 414, lower winding ofsupervisory relay 405 to battery. The winding ot relay 544 is of high'resistance and while it responds to the current flowing in this circuitwill not cause the operation of supervisory relay 405. Relay 544 inoperating locks relay 545 in a circuitindependent of the contactcontrolled by relay 546,

The dialing circuit may be traced from the ring conductor 1001, middleLipper armature and back contact of relay 1011, alternate contacts ofthe outermost lower armature of relay 904, lower winding of relay 905,front contact, and lower armature of relay 906, front contact and lowerarmature of relay 909, ring contact or' jack 900, ring contact ofplug401, lower normal contacts of ringing key 437. contacts 452 and 453,lower armature and back contact of relay 448, contacts 456 and 457,conductor 458, conductor 542, front contact and armature of relay 501,front contact and innermost lower armature of relay 547, -middle lowerarmature and front contact'of relay 547, conductor 553, dialingcontact-e554 and 555, conductor 502, conductor 511, conductor 433,contacts 434 and 459, back contact and inner upper armature of relay448, contacts 450 and 451, `front contact and inner upper arma-1re ofrelay 438, upper normal contacts of ringing key 437, tip of plug 401,tip of j ack 900, upper armature and lront contact ot relay 909, upperwinding ot supervisory relay 905, alternate contacts oi the upperarmature of relay 904, back contact and outermost armature of relay 1011te tip conductor 1000. Supervisory relay 905 remains operated in thiscircuit and holds relay 907 operated. l/Vhen the dial is released andcontacts 554 and 555 are momentarily and intermittently opened to effectthe distant incoming selector in a well-known manner, relay 905 willrespond to these impulses,

slow to release will maintain its armature attracted and thereforemaintain a ground on conductor 908.

During the dialing period a circuit is established from ground, thefront contact and outermost lower armature of relay 547 winding of relay556 to battery and ground. Relay 556 short-circuits the input of theoperators click reduction circuit-and therefore effectivelyshort-circuits the operators receiver so that she will not be annoyed bythe clicks produced during the dialing.

When the dial 548 has returned to normal,

lrelays 501, 507, 543 to 547 inclusive and 556 will all return to normaland the circuit will assume the condition schematically shown in F ig.16. When the dialing has been completed and the distant connector switchhas been set on the terminals of the called line, such called line willbe signaled in the usual manner and when the party thereat answers areversal of current will take place whereupon polarized relay 910 willbe operated. Relay 910 causes the operation of relay 911 which in turnbridges impedance coil 912 across the tip and ring conductors of jack900 and therefore across the windings of supervisory relay 405.YImpedance coil 912 is of low enough resistance to cause the operation ofrelay 405 to perform its usual function of controlling the supervisorylamp 403.

Station Vto Zeal central oce traf/zic Fig. 14 is a schematic of the cordcircuit established .in a. station to central office trunk connection.Fig. 17 is a schematicof this same type cord circuit with the dialingand talking key operated indicating the changes vwhich take place.during the'dialing period.

Assuming that the trunk of Fig. 7 `extends to a dial office, then, whenthe plug 400 is inserted in jack 700 a bridge including the middlewinding of relay 413 is thrown across theconductors 702 and 703 tooperate the distant line relay.

ln this case since relay 409 is not operated there will be no circuitthrough the lower winding of relay 446 for the operation of relay 546 inthe dialing circuit and hence relay 545 will not become operated asbefore. Therefore, instead of having a bridge such as the winding ofrelay 544 connected to the two upper armatures of relay 501 there willnow be a battery and ground connection through the two windings of relay543 connected to such upper armatures of relay 501. Therefore, duringthe dialing period when the cord circuit is split by the operation ofrelay 501, battery vand ground are still supplied to the calling stationthrough the windings of relay 543 in place of the battery and 0roundoriginally supplied from the central oflice trunk. The furtheroperations are in accordance with circuits hereinbefore described.

Trunk t0 repeating` tie Zine connection' Fig. 18 is a schematic drawingof a connection which might be established from an incoming trunk suchas that of Fig. 2 to a tie line such as that of Figs. 9 and 10. The onlything to be noted in this connection is that since the marginal relay409 is operated the low resistance relay 546 of the dialing circuitprovidinglocally supervised distant batteryV feed and said means beingresponsive to a third ltype of connection for providing'a through pathwithout series impedance.

' 2. i universal cord circuit having an answering cord and a callingcord, a relay for each cord and means responsive to the operation ofsaid relays in a first combination for maintaining said cord circuit asa local battery feed circuit, in a second combination for convertingsaid cord circuit. into a locally supervised distant battery feedcircuit and in a'third combination for converting said cord circuit intoa through path without series impedance.

3. A universal cord circuit having an answering cord and a calling cordandnormally arranged as a local battery feed circuit, a relay for eachcordand means responsive to the operation of said relays in a firstcombinationfor maintaining said normal arrangement, in a secondcombination for rearranging said cord circuit as a locally superviseddistant battery feed circuit and in a third combination for rearrangingsaid cord circuit as a through pathnwithout series impedance.

, 4. universal cord circuit having an answering cord and a calling cord,a talking since it is not wished to` path from cord to cord normallyarranged A as a local battery feed circuit, a signaling pathfor eachcord and a relay for each cord in said signaling path, and meansresponsive to the operation of said relays in a first combination formaintaining said talking path in its normal condition, in a secondcombination for converting said talking path into a locally superviseddistant battery feed cir-- cuit and in a third combination forconverting said talking path into a through path without seriesimpedance.

' 5. A universal cord circuit having an answering cord yand a callingcord, a talking pathvfrom cord to cord normally arranged as a localbattery feed circuit, a signaling path and a marginal relay therein foreach said cordl and means responsive to the oper ation of said marginalrelays in one combination for maintaining said'talking path in itsnormal condition, in a second combination for converting said talkingpath into a locally supervised distant battery feed circuit and in athird combination for converting said talking path into a through pathwithout series impedance. Y

6. A universal cord circuit having an answering cord and a. callingcord, a talking path from cord to cord normally arranged as a localbattery feed circuit, a signaling path and a marginal relay therein foreach said cord and means responsive to the operated condition of both ofsaid relays for maintaining said cord circuit in its normal condition,responsive to the` operated condition of either one of said relays onlyfor converting said talking path into a locally supervised distantbattery feed circuit and responsive to the operated condition of neitherof said relays for converting said talking path into a through pathwithout series impedance.

7. A universal cord circuit having an answering cord and a calling cord,a talking path from cord to cord normally arranged as a local batteryfeed circuit, a signaling path and a. marginal and non-marginal relaytherein for each cord, and means responsive to the operation of saidrelays in a first coinbination for maintaining said talking path in itsnormal condition, in a second combination for converting said talkingpath into a locally supervised distant battery feed circuit and in athird combination for converting said talking path into a through pathwithoutl series impedance.

8. A universal cord circuit having an answering cord and a calling cord,an answering supervisory relay and a calling supervisory relay, andmeans responsive Vtothe establishment of one type of connection forrendering said answering supervisory relay responsive to hookswitchoperation over said answering cord and responsive to the est-ablishmentof another type of connection for rendering said answering supervisoryrelay responsive to hookswitch operation over said calling cord.

9. A universal cord circuit having an answering cord and a calling cord,an answering supervisory relay and a calling supervisory relay, a sleeverelay for each said cord, and means responsive to the operati on of saidsleever relays in one combination for rendering said answeringsupervisory relay responsive to hookswitch operation over said answeringcord and in another combination for rendering sait answering supervisoryrelay responsive to hookswitch operation over said calling cord.

l0. A universal cord circuit having an answering-cord and a callingcord, an answering supervisory relay and a calling supervisory relay, alocal battery feed supply, a sleeve relay for eachsaid cord, and meansresponsive to the operation of said sleeve relays in' one combinationfor rendering said answering supervisory relay responsive to hookswitchoperation over said answering cord and said local battery feed supplyand in another combination for rendering said a-nswerinfr supervisoryrelay responsive to liookswitcn operation over said calling cord and forexcluding said local battery feed suprly- Y Y il. in a telephone system,a trunk circuit, line circuits, a universal cord circuit having ananswering cord and a calling cord, an answering supervisory relay and a.calling supervisory relay, a local battery feed circuit in id cordcircuit and a distant battery feed accessible over said trunk circuit,and means responsive to a line to line connection by said cord circuitfor rendering said answering supervisory relay responsive to hooksuiitchoperation over said answering cord and said local battery feed supplyand responsive to a trunk to line connection by said cord circuit forrendering said answering supervisory relay responsive to hookswitchoperation over said calling cord and said distant batterv feed supply.

l2. ln a telephone system, a trunk circuit, line circuits, a universalcor-:l circuit having an answering cord and a` callin@r cord, ananswering supervisory relay and a calling supervisory relay, a localbattery feed supply in said cord circuit and a distant battery feedsupply and supervisory means accessible over said trunk circuit, andiieans responsive to a line to line connection by said cord circuit forrendering said answering supervisory relay responsive to hookswitchoperation over said answering cord and said local battery feed supplyand responsive to a trunk to line connection by said cord circuit forrendering said aA svvering supervisory relay responsive to hookswitchoperation over said calling cord and said distant battery feed supplywithout affecting said supervisory means associated with said distantbattery feed supply.

13. ln a'telephone system, lines of different character, a universalcord circuit having an answering cordV and a calling cord, an answeringsupervisory relay and a calling supervisory relay, a local battery feedsupply in said cord circuit and a distant battery feed supply accessibleover certain of said lines, sleeve relays for said cords operable inaccordance with the character of said lines and means responsive to theoperation of said sleeve relays in a first combination for renderingsaid answering supervisory relay responsive to hookswitch operation oversaid answering cord and said local battery feed supply and said callingsupervisory relay responsive to hookswitch operation oversaid callingcord and said local battery feed supply, in a second combination forrendering said answering supervisory relay responsive to hookswitchoperation over said calling cord and said distant battery feed supplyand for excluding said calling supervisory relay and in a thirdcombination Vfor excluding both said answering and said callingsupervisory relays.

14. In a telephone system, lines of different character, a linlr circuithaving an incoming end and an outgoing end, a source of ringing current,means responsive to 'theconnection of the incoming-end of said linlrcircuit to one of saidlines for a'utoinaticallyfconnecting said sourceof ringing current to the said line, a circuit for by-passing a smallamount of ringing current to the said cutgoing end of said link circuit,and means fresponsive to the character-of the said lines vfordifferently affecting said'by-passing circuit. 15. In a telephonesystem, lines of different character, a cord circuit having an answeringcord anda calling cord, asource of ringing current, means responsive tothe connection of said calling cord to one of said lines forautomatically connecting said source of ringing current to the saidline, a circuit for bypassing a small amount of ringing current to thesaid answering cord, and means responsive to the character of the saidlines for differently` affecting said by-passing circuit. 16. In atelephone system, lines of different character, a cord circuit having ananswering cord and a calling cord for interconnecting said lines, a.relay for each of said cords', said relays being differently responsiveto connection with said lines of different character, a source ofringing' current, means responsive to the connection of said callingcord to one of said lines for automatically connecting said source ofringing current tothe said line, a circuit for by-passing a small amountof ringing current to the said answering cord', and means responsive tothe diiferentoperation of said cord relays for differently affectingsaid by-passing circuit.

17 A universal cord circuit having an answering cord and a calling cord,a relay n for each said cord, asource of ringing current, a relay forsplitting the cord circuit and applying said source of ringing currentt0 the said calling cord, ay circuit for by-passing a small amount ofringing currentv around the contacts of said ringing relay, and meansresponsive to the operation of said cordgrelays in one combination foroperating said'ringing relay and closing said by-passing circuit, in asecond combination for operating said ringing relay and maintainingsaidby-passing circuit open and in a third combination for opening thecircuit of said Yringing relay.

18. A universal cord circuit having an answering cord and a callingcord, a marginal and a non-marginal relay for each said cord, a sourceof ringing current, a relay for splitting the cord circuitand applyingsaid source of ringing current to the said callingcord, a' circuit forby-passing a small amount of ringing current around the contacts of saidringing relay, and means responsive to the operation of said cord relaysin one combinavtion for operating said ringing relay and and maintainingsaid by-passing circuit open and in athird combination for opening thecircuit of said ringing relay.

f 19. A universal cord circuit having an answering cord anda callingcord, a relay for each said cord, a source of ringing current, a relayfor splitting the cordV circuit and applying said source of ringingcurrent to the said calling cord, a circuit for by-passing a smallamount of ringing current around the contacts of said ringing relay andmeans responsive to the operated condition of both said cord relays foroperating said ringing relay andk closing said by-passing circuit,responsive to the operated condition of one. of said cord relays onlyfor operating said ringing relay and maintaining said by-passing circuitopen, and'responsive to the operated condition of neither-of said cordrelays for opening the circuit of said ringing relay.

' 20. A universal cord circuit having an answering cord and a callingcord, an answering cord supervisory relay and a calling cord supervisoryrelay, an answering cord supervisory signal and a calling cordsupervisory signal, sleeve relays for said cords, means responsive to afirst energization followed by a deenergization of said answering cordsupervisory relay for establishing a recall circuit, and meansresponsive to the operation 'Ofzsaid sleeve relays in one combinationfor connecting said recall circuit to said answering cord supervisorysignal and in another combination for connecting said recall circuit tosaid calling cord supervisory signal.

21. A universal cord circuit having an answering cord and a callingcord, an answering cord supervisory signal and a calling cordsupervisory signal, an answering cord supervisory relay and a, callingcord `supervisory relay, sleeve relays for said cords, means responsiveto a first energization, followed by a deenergization of said answeringcord supervisory relay for establishing a recall circuit,and meansresponsive to the operation of said sleeve relays in a first combinationfor connecting said recall circuit to said answering cord supervisorysignal, in a second coinb'ination for connecting said recall circuit telsaid calling cord supervisory signalV and in a third combination forrendering said recall circuit establishing means ineffective.

22. e. universal cord circuit having an an-A swering cord and a callingcord, an answering cord supervisory relay and a calling cord supervisoryrelay, an answering cord supervisory signal and a calling` cordvsupervisory signal, lines ofdifferent character, sleeve reiaysfor saidcords operable in accordance with the character of the lines to whichsaid cords may be connected, means responsive to a first energizationfollowed by a deenergiza-

